I'm going to assume you work mostly with Wiccan or other Neopagan groups. In those ones, yes, there's a tendency to find more women than men. On the other hand, Hermetic magick is often a sea of dudes. I think this has to do with the very different stylings of the two types of practice. Hermeticism is extremely forward and goal-oriented (very Fiery and yang) whereas a lot of Wiccan and Wiccan-influenced magick are about accepting divinity into oneself and living in combined harmony with All (very Watery and yin). These obviously aren't absolute distinctions, but they're pretty strong trends.

This is also what many of us mean when we refer to Wicca as "feminine." Not glorifying woman or the Goddess above men and the God, but being receptive and seeking to experience the Divine through Watery transcendence.

As a bonus, I believe this may also be why the moon is such an important part of Islam (their holy calendar is lunar and they circle the Kaaba in Mecca counterclockwise). Of the expressly Abrahamic religions theirs puts most emphasis on being receptive to God, existing in a state of oneness with other things, and honoring and respecting femininity, they're just also expressed very differently than we're used to. This may also be why a lot more women convert to Islam each year than men (the ratio is 4:1 I think).

Men don't usually broadcast it like women do. Most men who practice magick are less likely to make it known then women. Women seem to be more open about it, probably because they are naturally more social and expressive. I don't believe there is a gap. Many, including myself, don't like talking to other magickal practioners in person because most that are open about it are fluffy bunnies or novice. I used to frequently go to fairs and expos but I stopped because of how many wanna-be's they attract.

Men are more likely to practice higher magick and are either solitairy or are apart of a serious society like the Invisible College, Freemasons, or Golden Dawn.

I also think culture, tradition and the variety of practices play a large part in it too.

For instance, seidhr (a Norse magickal practice) was traditionally practiced by women and it was frowned upon for men to practice it (until recently). Thus, you'll see more seidhr-women and volvas than you'll see males. That's due to older tradition and culture moreso than anything.